Apparatus for showing pressure versus volume diagram



R. J. TINKHAM. FOR SHOWING BR 5 VOLUME DIAGRA I APPARA URE VER Filed Jan. 22, 1944 s Sheets-Shek 1 L oooo meg y 1948. .R. J. TINKHA'M 2,445,046 APPARATUS FOR SHOWING PRESSURE VERSUS VOLUME DIAGRAM "5 sheets sheet 2 Filed Jan. 22; 1944 y 13,1948! R. J. .TINKHAM 2445,945

KY'TARATUS FOR SHOWING PRESSURE VERSUS VQLUME DIAGRAM 5 Spats-Sheet 3 Filed Jan. 22, 1944 E J ETZu/q y 13, ,948. R. J. TlNK M 2,445,046

v APPARAT FOR SHOW URE VER S VOLUME DIAG Filed Jan. 22, 1944 5 Sheets-Sheet 4 121/558 ZZJJinkham.

July 13, 1948. .R. J. TINKHAM 2,445,046 APPARATUS FOR SHOWING PRESSURE VERSUS VOLUME DIAGRAM 5 Sheets-Sheet 5 Filed Jan. 22, 1944 fig. 8. 4

E m flvssell I fi'nkkan iv ii Patented July 13, 1948 APPARATUS FOR SHOWING PRESSURE VERSUS VOLUDIE DIAGRAM.

Russell J. Tinkham, Chicago, 111., assignor to Armour Research Foundation of Illinois Instb tute of Technology, a" corporation of Illinois Application January 22, 1944, Serial No. 519,404

4 Claims. (01. 73-115) This invention relates to improvements in ap-" paratus for showing a pressure versus volume diagram for a reciprocating engine or equivalent structure. More particularly, the invention relates to a device which may for convenience be termed a volume sweep generator and its use with associated apparatus to produce quickly-and accurately a visual pressure versus volume diagram, although the invention may have other uses and purposes as will be apparent to one skilled in the art.

When a. reciprocating engine is developed, and sometimes at later intervals during its life, it is highly desirable to have a pressure versus volume indicator diagram available to determine facts concerning the operation of that engine. Such a diagram denotes the frequency of the engine, gives facts concerning the valve action of the engine, the compression of the engine, shows undue restriction in air cleaners in connection with multi-cycle engines, denotes facts concerning the back pressure in mufliers used with the engine, etc. Heretofore, it was substantially impossible to obtain such data concerning each specific engine coming ofi a production or assembly line, such as is common in the manufacture of automotive engines in great quantity, owing to the necessary complicated, tedious, and highly expensive procedure that would be involved were such data formulated in connection with each 1 engine on the line; The best that could be done, therefore, was to run rather exhaustive tests on certain engines only, with the idea in mind that all other engines constructed in accordance with the same specifications as those tested would function suificiently close to the tested engines for practical purposes. Further, it has been heretofore unduly difiicult to obtain a substantially accurate pressure versus volume indicator diagram for any reciprocating engine, and it has always been desirable to materially simplify that process. Highly skilled operators were also essential in order to interpret the functioning of an engine and salient facts concerning its operation from a pressure versus volume indicator diagram. I

With the foregoing in mind, it is an important object of the instant invention to provide means sufficiently economical and which may be used sufficiently facilely to warrant the production of a pressure versus volume indicator diagram for each and every engine in a production line.

Another object of the invention is the provision pressure versus volume indicator diagram for a reciprocating engine.

Another object of the invention resides in mechanism forfurnishing a pressure versus volume indicator diagram for a reciprocating engine, which diagram is as accurate as is necessary for a particular job, the accuracy depending upon the construction of a certain part of the mechanism.

It is also a feature of this invention to provide an arrangement for visually showing at a glance a pressure versus volume indicator diagram for a reciprocating engine, and presenting that diagram in such a manner that even a relatively inexperienced operator can tell at a glance whether or not that engine is operating satisfactorily.

Another highly important object of the instant invention is to provide an arrangement for furnishing a pressure versus volume indicator diagram for a reciprocating engine, in which the diagram is a substantially accurate and actual diagram for a particular engine, and the arrangement is suitable not only for solid piston engines but also for flexible piston engines where the volume is not the same on the downstroke as on the upstroke for the same intermediate location of the piston.

It is a further feature of the invention to provide an arrangement for presenting a pressure versus volume diagram for a reciprocating engine, and which arrangement is good for all engines from the same assembly line, or for all engines which the particular manufacturer intends to be substantially identical.

Also a feature of the invention resides in the provision of mechanism for providing a pressure versus volume diagram of an engine, in which mechanism the most changeable item of equipment results from measured data which, if made with reasonable accuracy, should suflice for a long run of engines intended by the manufacturer to be alike. I

Still a further object of the invention resides in the provision of apparatus for use with a cathode ray oscilloscope to show a fluorescent trace in the shape of an actual pressure versus volume diagram for that particular engine.

It is a further object of the invention to provide apparatus for visually indicating a pressure versus volume diagram for aparticular engine, in such a manner that engine characteristics may be determined at a glance from the diagram, and yet the diagram or data provided by it may be easily recordedif so desired, but in ordinarypracthe instant invention;

Where all cylinders are intended to be identical, is so small as to be negligible.

Referring now to Figure 1 a portion of a reciprocating engine I is shown and in this instance a cylinder 2 of that engine is under test. Connected to the cylinder by a suitable conduit 3 is apressure pick-up device 4., which maybe a com mercially available transducer. As a specific example, this device may be designed to measure pressure from 0.1 pound per square inch to 1,000

pounds .persquare inch over a frequency range acteristics and advantages of the instantinven-i.

tion have been above pointed out, others will, become apparent from the'following disclosures,

taken in conjunction with .thewaccompanyihg drawings, in which Figure l is a fragmentary schematic layout of equipment connected to provide a visual pressure versus volume diagram for a reciprocating engine, theapparatus embodyingprinciples of Figure 2 is. an enlarged' fragmentary central vertical'sectional'view; withiparts s'h'own'in elevation, 'of'a' portion "of thea'pparatus of'iFigure' l,

namelythat portion. whichmight'forconvenience be termed a volume sweep generaton seen-"in the central part ofFigure 1';

' Figure 3"is a" topplan viewof' the" structure'of Figure 2, withparts broken away and with the casingremoved;

' Figure '4 is fragm'entary'vertical' sectional view taken substantially"sis-indicated by t-he line 3, looking-in the direction of thearrows;

" Figure 5' 'is a' schematicdiagram- "illustrating showing'the connectionsifor tjheappa'ratus of "Figure'l.

"As shown onthefdrawings Figure 'li there isjsh'own' a general'assembly of apparatus capable" of producing a visual pressure versus volume.diagram of a, reciprocating engine, andis'highl'y desirabl'effor use with a high speed reciprocating. engine. '"The' indicat-- ing diagram. is shown directly as a fluorescent trace on a cathode ray oscilloscope screen.

In the. use of thepresentl invention; for best and. most complete. results, itisdesirable toob- .tain a. diagram for each cylinderof. the engine,

if the engine is a multi-cylinder structure. In someinstancea -it. may be possiblesto. work :on the assumption that. all: cylinders perform alike; and therefore itvis =only necessary toobtain azdia ram for: one of thetcylinders; .However, it. requires little more time to.-obtain-.a;idiagramfor each of the cylinders and-obviously such procedure results in a better complete-picture of' the-functioning of the 'pa-rticularengine. It' i's'not necessary in quantity manufacture of engines, however, *to

alter the device for eachenginecylinder. The smallamount of error occurring between the volume of one cylinder-and that of another,

fr,om:5, tog2, 000cycles per second, and the voltage output of the device may be proportional to pressuresomewhere within this range and may equal approXimately"0:03 peak volt for each pound per square inch ofpressure when operated into an impedance of. substantially 10 megohms.

Such a device. may be purchased on the open market.

' "The pressure pick-up 4 is connected through a pair of conductors contained within a shielded cable 5 -to-- a commercially availablevoltage amplifier 6 pr-eterab-lyeithen. tin-alternating cur.- rent: or. a direct current vacuum tube amplifier having negligible or: zero-phase shift between input signal and amplified: output signal. Itz-may be desirable to-use an. alternating currentampli- .fier for high speeds, andadirect current. amplifier for lowspeeds, suchzas. below lil. cycles per second.

The: output: of the voltagepamplifierifi; may -.be connected through. aisuitable: .cable:?l directly..to the vertical deflection plates of; a. .cathodeeray oscilloscope. 8. P'Ifhis oscilloscope:ymaysbfiuoilany suitable. type .iiproperly -connected :withzthefirest of' the apparatus; :As ...a. p-specific example-la .cathode; ray oscilloscope .havingr:.all.;deflection plates isolated willrgive-ihighlw satisfactory and very flexible I results: zSuch-l an; instrument: may also be obtained onfthempenimarket.

The internal moving; partof a; device; termed for conveniences. volume sweepggienerator -and generally indicated: by numeral :9, 1 is; connected: by

means of a shaft .Ifl, a. coupling; H;,;and;-another shaft I2,.-to the crankshaft ofgthe engine 1. This device 9. will be .more fully :later described herein. The volume sweep generator 9; may be-electrically connected, with a. vacuum tuber-voltage amplifier l 3'; preferably an: amplifier with. a selfcontained powersupply. As a specific-example, a two stage resistance coupled voltage. amplifier having the same general characteristics. as. the amplifier: i5. is: satisfactory. Theoutput of this amplifier is directly connected throughas-uitable cable, M with the. horizontal-deflecting. platesof the oscilloscope 8L" When -the apparatus. is energized and, the

engine I is. inoperation, a fluorescent trace in enlarge'any part'of the fluorescent'traceor diagram for detailed study:thegamplifier- -fi should,

of course, have suifici'ent voltage gain-f ion that purpose. V

It should also be appreciated that while-in Figure l :the entire'apparatus has been illustrated in a rather "spreadput'manner for the purpose of clarity, all of the apparatus-save the pressure pick-up 4 the cable 5 the mechanical connection through thecoupling H, and the customary connection to a suitable source-ofpower supply, may

such a container, it is only necessary to provide specifications i I casing wall through or shafts extend may through an opening 3!} in I I housing for connection'to the aforesaid amplielectric tube 21, with narrow, extending in of the photo-electrictube. I

partition 3| above the optical slit is an opaque bjflAt' 39 is secured to the partition 31- as-indicated at 40.

activeduring' operation. conductors 43 and4'4 t'o connect' the"socket to ready-access torn-e volume sweepgenerator! so that this generator fmay j be altered-in a manner to be later described to accommodate engines of different types; sizes; or I built under different With reference to' Figures 2, 3 and 4, it will be seen that the volume sweep generator -9 includes a suitable casing or cover'flearranged toenclose three sides" and the front of the-apparatus, al-

' though this cover may-be constructed in any manner suitable for the purpose.

The structure enclosed 'withinthe coverl-Binclhdesa bottom strengthening frame I! to which is-secured a suitable side wall formation I 8 carrying a transverse partition |9 completing a structure in the nature of an inverted I I 20-, however, extends substantially the full height The inside of the'caslngl and box. Theback partition of the device.-

the {surfaces of all partitions within the' casing are preferably paintedflat'black, and the'icasing;

is preferably lightproof. Any apertures" in the which electrical conductors be 1 treated in any suitable manner to render them lightproof,"if necessary. Carried by suitable supports 2| extending inwardly from the rear wall 'is a bracket arrangement including a backing member 22 bearing a pair of vertically spaced'resilient clamps 23 and 24 provided withterm'inal connections 25 and 26 respectively; The clamps removably support a=- suitable photo electric I 'tube'- 21," the conductive clamps engaging the terminals of the tube.

cable28 containing-separate conductors connected to the terminals 25 and 26 extends through an opening '29 in the floor platform [9 and out the rear wall 2|) of the Disposed in front of the photo el'e'ctric tube 21 isan upright partition 3| I I across the casing so as to black out all light from the oppositeside'of the partition from the photo- I the exception of that light passing through an optical slit 32 in the partition 3|. This optical slit isirelatively elongated and a vertical direction in front On the back'of the slide33provided with a suitable slot '34 for engagement over'the'sha'nk'of a; securing bolt 35 by means 'of'which the slide mayberaised and lowered to "vary 'the heightof the 'optical'slit as "may be required. Itwill' be understood that the j width'and length or the independently variable by optical slit jaws. if'so desired." E .With referencefmore particularly optical slit may be each means of conventional I to Figure 3,

it will be seen that' a pair of angle partitions '35 and 31 extendingfrorn the floor partition l9 to containingthe optical slit. The

through which light from a source to' be pass -toward the optical slit forward end of thech'annel 38, a bracket This bracket' supportsa socket 4| for an incandescent" laihp 42 which rovides a source of light'to maintain the photo-electric tube 21 'It has suitable electrical which, extends entirely wall of the'casing slit 32.

sweep generator 3 is a and remains so flxed during the use ofthe device,

any suitable source of electrical energy. These conductors'may be enclosed in a cable 45 extending= throughan opening 46in the floor-partition leandiexiting through another opening 4l inathe side wall of the housing. I

So far, the described structure of the volume relatively fixed structure,

except for possible adjustment and replacement of'parts when necessary. The movable parts of the volume sweep generator are designed tovary the amount of light received by the photo-electric tube 21 from the light source 42 in keeping with variations in cylinder volume of the particular engine under testthroughout the piston cycle, and thus'produce upon the cathode ray screen of the oscilloscope a pressure versus volume indicator diagram of that particular engine.

These moving parts include the aforesaid shaft III which extends through an opening in the front It and passes through a pair of bearing mountings 48 and 49 on the floor partition l9, collars 50 and 5| being utilized to maintain the shaft in a proper position of adjustment. As seen best in Figure 2, the shaft Ill extends through the light channel 38 beneath the light source 42 to a position adjacent the partition 3| containing the optical slit. The inner end of the shaft carries a suitable holding collar 52 into which is engageable a. plurality of attaching screws 53.. opaque, preferably metallic, disc 54 and another disc 55, which discs extend through a suitable slot 56 in the floor partition Hi. It will be noted that the opaque disc 54 is on the side near the light source. 1 v

The disc 55 is preferably of substantially transparent materialsuch, for example,ias celluloid or photographic film stock. This disc 55 asbest seen in Figures 4 and 6 has an opaque area :51 thereon, which area is eccentrically disposed'relatively to the shaft Ill. The disc itself is symmetrical about the shaftlfl, that istheshaft I0 extends through the exact center: of the disc in the preferred construction, so that the rotating apparatus will always be in balance; The eccentric opaque area 5l may be painted upon the disc, or in the-event it is a photographic film the opaque area may be provided thereon by conventional photographic technique. I A

It .will be noted that the disc '55 is disposed adjacent the partition 3| in a parallel plane therewith, and overlies the major portion of the optical In order to'maintain the photo-electric tube 21 energized properly at all times there will be a relatively sh'ort portion or the optical slit above the disc 55 and below the adjusting slide 33 always open, as seen in Figure 4, so that some light from the source 42 always reaches the photoelectric tube. -In a preferred arrangement, it is -desirable tohave the disc 55, partition 3|, and :photo-electrictub'e 2-1 as close together as'is reasonably'feasible. I r

The opaqueportion' 5l-of the disc 55 is so'designed that when the disc is rotated in-front of the optical slit, the effective length of the slit "is varied from a maximum to a minimum value I indirect proportion to the changes of volume ofthe cylinder under test during rotation of the crankshaft of'the particular'engin'e. As stated above, the shaft M of the volume sweep generator is coupled to the engine crankshaft so as'to be driven atthe same speed as the crankshaft of theengine under test. If so desired, a gear train may be employedfand amultiple or s'ub' multiple This structure holds in place an mi ithe .engine speed may-he :used. cihccordingly,

aszthe: volume 10f the particular cylinders changes during. the atravel :of the :piston .=,through tits. .re- .ciprocation cycle the effective. part .ofxithenoptical slit is proportionately nvaried 1inisizeiand1-the photo-electric :tube is correspondingly affected.

=Eor engines of 1: difierent; sizesnori of. different types, different discs -55.: :mustibenused. rFforglall necessary to produceormake a discg55 for awparconcerned; is absorbed in the :testingyof a 360mcplete line .or. run oficlentical enginessso there' is ibut :an infinitesimal amount of' that work 1" attributable to thewtesting .of .each engine.

1 The making .of the :masking disc @515 for .a. run of engines "should be donev with due care-and 1 caution. A preferred .methodpfi making thiszdisc includes first determining the cylinder volume ,at Warious degrees of crank angle in :whatever increment may be predetermined, dependingupon ithepdesired accuracyeo'f result. 'Forxvery g'accurate awork,ithe 'cylinder:volumemayzbe:determined .z-inwincrements ofmnedegree of :crank anglazand v:for;slightly lesser :accuracy but which imayzibe'j satisfactory for most cases, the cylinderryo'lume could be determined. in incrementszoffi degrees of JCIflI'lk angle. *Thatis, thevolume ZOffthGiCYlil'l- :der is =;determined as it :varies sbywvirtue :of the movementofithe. piston therein :at'i specifiedwin- .crements vdu ring one revolution {of l the. cran'lzshafts i Certain :other data must be 1' at Ehand including vthemaximum'dimension of the photo+tube phhtopasensitive plate, the: maximum .and minimumavalrues :ofthe cylinder 'volume; and the 5 distance from -.the reenter .of the photo-tube .nphoto-sensititre -;plate. .to :the .:center of. rotation -of .the', masking disc. -With thesepifiguresrthe radius of therresulting masking disc-may readily 'be :detfermineduforthe particular volume sweep generator. i

. A'large -chart-sis then made oni-which thezrotat- :ing. .center,;of. .the :ultimatesdisc; -is.. used as ;;the act-inter of'ithe chart, ,asiindicatedgat:58:in Figure 5.

ilmana'ting" from. t'hisgcenter are radii lineslceSiL;z v,onetfor-each of therselectedlcincrements"of vcrank.

rotation.. Knowing the; ultimate 'required size aDf ;:diSC,itl1e various .cylinder--yo1umes ;aremlotted on each of :the radii lines; 59 ,by v simple arithmetic proportions, =1 starting 5 with the larger :yolumeg at x60 enointffi ll. inr Figure 5: corresponding to; zero "on-360.

.The "cylinder volume :will therrqbecjome; flessizuntil at point 6|, or 180, the smallestqyolume'occurs, and from this point -.ba-ck.to the-starting point the volume again gr 2 isgdrawn through the pointsthusiplotted; the .curve, bemgimade as; smoothly as possible. .;.-It, is

,better during :the :preparationof :the.;;ch'artto ,put .-;in a central :cirjcle i 63 to markithe 1 center of rotation of the-ultimatej-masking:disc. ,Inyorder;

to clearly ,.and:-;easi1y establish this, center-,stwo otherf-OiIClES 1 concentric; with the arole-:63 imay 'als'osbegfdrawn as indicated .at "6 4 and::-65. -After the circle-:621qhas (been made, the..:p01?tion; on the actually v increases. A Milt-Vein jticular xengine, cylinder, "while; possibly tprohibitiyely. expensive except, in 308593 .ofspecialgtests .7 20" :forres earch work insofar as a. single,cylinder:...is

lbennkediormaintedi preferably iblack. .Thei pace between:. the woineles -63 .iand -M .-mayv. likewise zbe treated. care should. beytakensso that; the poutlineyof -,-the. :blackened area will be smooth,

By making such a chart much largerlthan will -.1ultlmately he used; small -variances {in :the black- Eened :area 1 5 1 @will .;be rendered substantially, lunnoticeableawhen ithe ilarge charms, zphotographlcallyreduced. The. largechartmay be photographed ,with theaid: :of 'a suitable camera :to. the desired: size, depending. :npon the required-ire- .sultantsiZeaot-the masking disc. .o'lhe negative is developed; land; a; positive .contact FDrint made from that: ene atiue -on jphoto-sensitive material whacked upon .eany tdesi-red;atransparent; or trans- .glucent backing w-material, ,such as .Celluloid, standard photographic@fllmwglass .plastlc, etc., sedated withsa.whom-sensitivenemulsion. ..In the ;@photographic;technique:employed, itiis desirable to; obtain as'.=muoh =z1contrast,.sas lpossibl-esand good definition.

Fromathe tfinishedgpositiye 1a icircularr masking disc .55 of ,the proper radiussisycutrusing tharotaationcenter. point,-.58 :-as the. centerlof thetmasking ;.disc. thus, (leaving the; darkened ..ar ea v 51; eccen- .,trical1-y disposed lonmtheacliscr was seen .best ,in Eigurefi. .This finishedtmasking disc .may .then be punched centrally to.,.,accommodate,tthe shaft Jil,and-secured.intnositiontas seen in Figures 2, .3 land .against the opaque disc 54.

-It, isinot necessarytm follow.theeabove described method .specifically,:. because; the: negative. itself may beusedtas themaskingdisc. .LIn thatvevent, .-the area .51" wouldbe rsubstantially .transparent, and ..there would jbe. ..a darkened aborder themaround. ,kltcmakes ,noreal-udifierence if .the eccenltric 'portion.5 1..is darklorllightland the boundary therearoundlight or dark respectively, asthedisk varies the amountof light falling, onthe photo .cell, .and, such variation maybe .;in ,.either Jdirec- ."tiongwithout affectingtheope'ration. dffthe. device. 'i;'Ihe.same...masking disc may." be aisefch'forall. .eng'ine Jcylinders -inter1'ded.,.by-.-.the' manufacturer ,to fibre identical. If .an engine Lhaying .lcylinders ..of different type or different size. is .to 'be tested, a

. new masking disc: mustbe made'ltoifitthosedifferent cylindersfiif reasonable. accuracyisi desired.

in Figure 1.

In Figure 9? I have illustrated diagrammatically a, wiringdiagramiforlthe 'apparatusshownmainly It will Lhe. .seenithat. Lthepressure pick-up device. his, inonnected .througnapair. of

conductors .661 .anc1;6.'|,;to. the .Moltage amplifier )6. llllhese..conductors.are. contained within. the lcable effects from outsiiietqdistuitbances.

. 5 .of iigurefh-lwhich-l cableisshielded as indicated cat. '68 .inILEiguIe J91 to .eliminate any. undesirable The. .voltage amplifier .6 is connected ,through. .conduetors' 69 .an'dfi'm contained within came-11,10 ;the vertical vdeflecting plateslof the oscilloscopejli. ['A -.dott.ed .line .encloses ithe:structure contained. .withinthe .volumesweep generator-.3101.purposesioflclarity. ll-helightrsource .42 iscconnectedthrough .conductors-143 and. to. asuitablesourcenf energy. such asl -a lbatteryg'l ii. Conductors 12landcll3stap ,the conductors and. '44 respectively. .andllead Finto 213,118 voltage-amplifier! I 3. The, .DhDtQaGlBGtIiC .tube i2 fl... is tconnectedibyz. way :of-.;conductorsl4 rand-11.5, contained within the cable 28, to the voltagetamplifier 1 3,;ethe cable enta lso. beingeshielded as iindicatedlat .15. Theiiloltagez amplifier-nas stated (above, is preferably;of thevt n iccarrying its own ,power supply abut c. .Figure :9,- f or ;.purposes tof iclarity, :the powem-supply has/been shownesepay matefromitheamplifler. lnathis flgure thepower .phartibetween thei ciificlefitanclthe circle fii'may. jsvsupplyzis :indicatediihy numeral-i H. and-his .con-

ensues nected to thevoltage: ampiifier by conductors 18 and 'l9. Conductors ;;8 0 and 8! lead fromthe power supply to gany suitable source of energy such, forexample-as 110 volt 60 cycle alternating current whichmay ea-sily'be hadby way ofany convenience outlet. The voltage amplifier i3 is connectedbyway. of conductors 82 a and 83 to, the horizontal.ideflectingplates of the oscilloscope '8 I so astoprovide the volume sweep in the resultant 1 fluorescent trace. Asseen best in Figures fluorescent trace made undertest of that engine will equal diagram 84. Reference. numeral 85 indicates the minimum .tolerable diagram for the class of engine under testy In other words, this pressure versus volume curve is the poorest that will be allowed for the particular class of engines being examined. The diagrams 84"and 85 are put on with' 'any suitable form of paint or ink and remain-in permanent position.

Accordingly, if the fluorescent trace appearing upon the screen l5 of the oscilloscope when an engine cylinder is under test falls betweenthe diagrams 84 and 85 the operation of that engine cylinder is satisfactory. Accordingly, it will be at once noted that an expert eye is not necessary for the testing or examining of a series of engines upon an assembly line, because even an unskilled operator is capable of telling whether or not the fluorescent trace falls between the perfect diagram and the minimum tolerable diagram. It is not essential that that operator even know all the information available from an indicator diagram. On the other hand, if the test is made in research work or is a special test, a skilled analyst may be used to examine the fluorescent trace from which he can tell the efficiency, the compression, the possible valve action. undue restriction in an air cleaner, back pressure in mufflers, etc. In Figure 8 I have indicated a curve 86 in dotted lines, as exemplary of a fluorescent trace appearing upon the cathode screen of the oscilloscope and which falls satisfactorily between the ideal curve 84 and the minimum allowable curve 85. The dotted curve 86 would indicate that the cylinder under test was sufficiently satisfactory for commercial purposes.

In operation the instant invention is extremely simple, economicahand highly efficient. Assume that tests are to be made of a series of engines intended to be idenitcal coming down a production line. The apparatus of Figure 1 may be disposed adjacent to termination of that production line so as to meet each engine that is considered finished. Assuming again that the engines are multi-cylinder engines, it is a simple expedient to connect the shaft I of the volume sweep generator 9 to the crankshaft of the engine, and then connect the pressure pick-up 4 to the first cylinder of the engine. When the engine is operated, a fluorescent trace which is a substantially true pressure versus volume diagram of that engine land 8 the cathode/ray screen. l of .the oscilloscope is providedwith Also prowill appear upon-the screen l5. If that vtrace; 84 and85, that particu' I lar cylinder is satisfactory. Such operationrefalls between the curves quires onlya very small interval of time. Upon the completion of that test, the pressure pick-up 4 is connected toxthe ,next engine cylinder and to the crankshaft of the engine to maintain the proper phase the shaft I2 is shifted relatively relationship between the pressure. and volume changes in the cylinder. successive engine cylinder is examined, and in like manner the following engine is tested.

Of course, it is tobe understood that a masking disc 55 has been made for .the particular engines under test; If the sameapparatus is to be used upon-another production line making engines of different types or, different-sizes, a

masking discfar that particular type or size of engine must be installed in the volume sweep generator 9.

It will be especially noted that the ap aratus will work equally as well for single cylinder "en'- gines as for multiec'ylinder engines, and equallyas well for flexible pistons as'rigid'pistons. In connection with flexible. -pistons, it will be noted that the cylinde'r volume on the, downstroke is not the ,7 same asit is on the corresponding locationuofthe, piston on the upstroke, but such variations will all appear on the eccentric pcrtioncf the'imasking disc. and will be accurately reproduced 'inthe fluorescent trace on the oscilloscope screen; i

From the foregoing, it is apparent that Iihave' provided'novel, economical, and highly eflicient means for obtaining. a substantially true and actual pressure versus volume indicator diagramfor engines, the invention being so economical in construction and use as'to warrantthe testing or" examining of 'each'cylinder' of each engine 'in 'a production line, and this is especially true because in such work the labor amounts to little and the services of a skilled operator for taking the readings are not necessary. It will also be noted that I have developed a new and novel method of producing a salient part of the apparatus which is suflicient for all engine cylinders intended by the manufacturer to be identical. Substantially any degree of accuracy may be obtained depending .upon what care is expended in the making of the masking disc.

It will, of course, be understood that various details of construction may be varied through a wide range without departing from the principles of this invention and it is, therefore, not the purpose to. limit the patent granted hereon otherwise than necessltated by the scope of the appended claims.

Iclaim as my invention:

1. In apparatus for producing a visible pressure versus volume indicator diagram for an engine, an oscilloscope, a pressure pick-up connectable with a cylinder of an engine under test and with one set of deflection plates of said oscilloscope, a photo-electric tube connected with the other set of deflection plates of said oscilloscope, a source of light for said tube, and means arranged proportionately to changes in cylinder volume during a piston cycle connectable to the crankshaft of the engine under test to be rotated thereby and positioned to vary the light from said source on said tube, said means being in the form of a masking member permeable to light having an opaque area eccentric'ally disposed relatively to the operating center of said member and which area has an outline in the nature of a curve vary- In that manner, each,

7 lling inaccordancewith volume changes in themgine cylinder duringjmovementof the piston.

2. In'apparatus for producing a-visible pressure versus volume indicator diagram for anengine;

an'oscilloscope, a pressure pick-up connecta-ble with a'cylinder of an engine under test and-With oneset of'defiectionplates-of said oscilloscope, a photo-electrictube connected with the othersetof deflection plates of said oscilloscope, a-source oflight for saidtube, and means arranged proportionatelyto changes in cylinder volume during a piston cycle connectable to the crankshaft of the engine undertestto be rotated thereby and positioned tovarytheli'ght from said source on said tube, said means being in the form of a masking disc having a-substantially transparent portion and an opaque portion, one of said portions-being eccentrically disposed relatively to'the operating center of the disc with'its outline varying proportionately to volume changes in the cylinder ofjth'e engineunder test.

3.' -Inr.a;pparatus for producing a; visiblexpres sure versus volume indicator diagram for an en.- gine, an oscilloscope, a pressure pick-up connects abl'eiwith a cylinder of an. engine -under= testya'nd with one set-cf deflection plates of said oscilloscope, -a, photo-electric tube connected with the other set of deflection plates ofsaid. oscilloscope,

aisource of light for said tube, and means arranged 1 30+ dur ngaapistonacycle connectable to the crank;

proportionately to changes in, cylinder volume shaitlof the enginev under test to be rotated thereby and: positioned to vary the lightfrom said source ionsa-id tube,;said means being in the form;

of'a'disc oi photographic film'having a'substanftially'transparent portion; and an opaqueportion; one or i said portions beingveccentrically disposed relatively to -th :centerof rotation of saidad-iscz I 5 Number:

eastward 4. A volume I sweep; generation-including a casing;a'photo electric' tube-in said casing, a light source for said tube, v a substantially transparent and rotatable masking: di'sm positioned betweenthetube and light source, said disc having a, substantially opaque: portion the outline of which varies'inproportion tovolume changes in an en sine cylinder during a piston cycle, said 2 portion being eccentrically: disposed relatively-to the center of the disc, means to connect. said disc to the crankshaft of an engine: under test for actuation thereby, an opaque partitionbet'ween saiddisc and said tube, said partition having a; slot therein,

means to selectively varyuthe length of said slot,

and'said' tube being -conn'ectable to an indicating apparatus. BTUfiiSEItL J. REFEBENCES CI I'ED. The foll'owing referencesare =01 record in the file of this patent: V

' UNITED, STATES, "PATENTS Name MacGregor-Mc'rris et' al'.

Number Date- Apr:28, 1925. Qs't1t0lenk; Man: 11,, 19:30,

Demontvignier Jan: 12', I937 FOREIGN-PATENTS Country Date 465,306,.

Schlesinger Dec; 31, 1940" Mari 24,1942

Great: Britain .Ma-y,3, .1937: 

